Jira Cloud instances merger

We have two cloud instances C1 and A1. We are planning a migration activity to merge C1 instance into A1 cloud instance. We are using Jira cloud migration assistant app to migrate the data from C1 to A1 instance, but we cannot migrate the “GitHub for Jira” app data. We would like to know the steps to migrate the data from C1 instance to A1 instance.
Please let us know the migration steps and provide us with the best possible suggestions

Thanks,
Saikiran Bommerla